[Tweeters] Turkey Vulture Migration (Second Attempt)

[Carol Riddell via Tweeters]

Dear Tweeters,

(I have converted the message I sent last night to plain text with the hope that it will be readable in today’s digest as I think the Cornell Birds of the World information on migration will be of interest. Apologies to those who will receive this twice.)

Those of us who have been on Tweeters for many years and have even shared Mason County Mountain Quail sightings, know Mary Hrudkaj to be a knowledgeable and respectful birder. It was with disappointment that I just read Jim Betz's unfortunate response to Mary's posts about migrating Turkey Vultures. 

I am sharing the following information from Birds of the World, as it informs us about Turkey Vulture migration across North America. Note that British Columbia has a peak migration in early September, which means those vultures are passing through Washington about now—both flying south and migrating. Also note that Washington is included among the states that see vulture migration between September 1 and October 23.

“Apparently individuals leave their breeding areas in North America between late August and early November, but early and late season migrants are often hard to distinguish from summer residents and overwintering birds. Eastern migrants (subspecies septentrionalis) from Ohio and Pennsylvania begin their outbound migration around 28 September, but the average departure day is around 24 October with latest departure around 12 December (n = 13, 160, 211). Traditional communal roosts often swell with the arrival of migrants, and serve as staging areas in the north; numbers are generally higher and for a longer period in fall than in spring. In southern Wisconsin (Baraboo Hills), the arrival of migrants is first evident in early September, with numbers peaking in mid-October (e.g., one summer roost of 60–130 birds grows to 200–280 individuals). The latest departure dates are related to the mildness of weather, and range from 26 October to 16 December (1986–2005, median 12 November, n = 11), and progressively later as population has increased and late autumns have become warmer (last departure dates for 1966–1985 were 6 October–26 November, median 22 October, n = 18) (212, 213, M. J. Mossman). In Ohio, migration begins around 15 to 25 September with the largest movements through 15 October (up to 270 counted at established roosts; 154). Migrants depart from northern and central Ohio counties by around 25 October to 5 November, and from southern counties by 15 November (154). Fall migration of central migrants in Saskatchewan (subspecies meridionalis or intergrades) starts on 3 September; the average start day is around 29 September, but some individuals depart no earlier than 12 October (n = 12, 160, 211). Migratory individuals in western North America leave their breeding areas in Washington, California, and Arizona to begin their outbound migration between 1 September and 23 October with the average start day around 4 October (n = 28, 160). In British Columbia, migration peaks in early September, with most birds departing by late October (158); at Becher Bay headlands (near Victoria, British Columbia), numbers peak during the last 10 days of September, and all birds have departed by mid-October (214). The duration of fall migration in eastern (subspecies septentrionalis), central (subspecies meridionalis), and western (subspecies meridionalis) North American birds averages 24 days ± 2 SE, 45 days ± 3 SE, and 17 days ± 1 SE, respectively (n = 53, 160, 211).”

Carol Riddell
Edmonds, WA